1. Field of the Invention
The present invention relates to an image data read out system. More particularly, it relates to a read out system for reading out the image data stored in a predetermined area (below, window) of an image buffer memory in response to an instruction from an image processor.
2. Description of the Related Art
In a digital image processing system, an image processor reads out image data from a window of an image buffer memory having n columns.times.m rows. As one example of the processing operation, the image data read out from the window is processed based on a "local operation", for example, "spatial filtering". In this case, the reading out operation from the window must be performed with high speed since the amount of data stored in the image buffer memory is very large.
Conventionally, a special computer is provided for achieving high speed local operation. Such a special computer has a pipe-line structure and comprises special hardware having a special function in accordance with contents of the processing operation. However, it is troublesome to provide the special hardware in each content of the processing operation.
Recently, a microprocessor has been used as one countermeasure to the above-mentioned problems. The microprocessor may be a general type and is controlled by a microprogram. According to such a microcomputer, it is possible to realize various image processing operations by rewriting software in accordance with contents of the processing operations.
In such a microprocessor, however, the processing speed is considerably reduced when performing a complex image processing operation since a complex microprogram must be rewritten. For example, nine access operations by a general type microprocessor are necessary for reading out the image data from a window having a size of 3 (columns).times.3 (rows).